1. Field of the Invention
The present invention relates to controlled actuator mechanisms and more particularly concerns improved control of operation of such mechanisms.
2. Description of Prior Art
Controlled actuator mechanisms are used in a number of different applications and are particularly useful in aircraft for initiating various types of emergency operations. Commonly, an explosive charge is employed to perform emergency functions with maximum certainty and minimum delay. Thus, upon occurrence of an emergency, detonation of an explosive charge is initiated by a controlled actuator mechanism and emergency procedure, such as removal of a canopy of a pilot's compartment, ejection of a pilot's seat with the pilot therein, release of restraints holding the pilot to the seat, and release and deployment of a parachute for recovery of the ejected pilot are carried out. In many of these applications, and in particular for release and deployment of the parachute, it is necessary that the desired emergency action does not occur unless the pilot and his parachute are below a predetermined altitude, even though the command to accomplish the emergency, procedures occurs at a considerably earlier time. Accordingly, actuators of this type must be controlled by a command, which commonly occurs when emergency procedure is desired to be initiated, and in addition, by a pressure sensitive device.
It will be understood that emergency initiators and actuators of the type under discussion are generally used but one time. Nevertheless, they are carried about for long periods of time, and, for such long periods, must be in a continued state of readiness. This long inactive period of constant readiness considerably intensifies inherent problems.
In some prior art mechanisms, wherein a cartridge is fired by a firing pin that is powered by a stressed spring and retained by an aneroid cell, the device is assembled in cocked position and thus additional safety devices must be provided to prevent premature firing of the explosive. Even with the use of such safety devices, the continual presence in an aircraft of a cocked or armed explosive device is highly undesirable.
In those devices of the prior art that are barometrically controlled, the sensitive pressure responsive aneroid generally is directly connected to a trigger mechanism as by a pin connection or the like. This connection imposes a continuous load upon and restraint against the ordinary motion of the sensitive pressure instrument and may significantly degrade its operation. Because the sensitive instrument cannot move freely in response to pressure variations during a major portion of its life, its operation may not be reliable when it is finally called upon to trigger the initiator.
One solution to the danger of the pre-cocked explosive initiator is suggested in the U.S. Patent to Roberts et al, U.S. Pat. No. 3,142,958 wherein a parachute release mechanism is operated by the firing of an explosive charge. Detonation of the charge is initiated by a firing mechanism that is cocked or armed as an incident to the generation of power in a pilot seat ejector mechanism. Thus, when the seat ejection mechanism is actuated, power is applied to the parachute release initiator to move a firing pin and a hammer against the action of a firing spring into a cocked position. When the firing pin and hammer are moved to the cocked position in this arrangement, an aneroid controlled sear pin is engaged by the hammer which is then held until the aneroid, in response to a decrease in pressure, operates a trigger mechanism to release restraint on the sear and allow the hammer and firing pin to be driven under the action of the compressed spring. In the arrangement of this patent, the aneroid control element is at all times connected to the sear restraining trigger and consequently is always subject to the load imposed thereby throughout the inactive life of the device. This restraint may severely compromise both accuracy and reliability. Further, cocking of the device requires a relatively complex interaction and motion of the sear and hammer since the sear must pivot in one direction to permit the hammer to move into restraining engagement with the sear. Motion of the sear in the opposite direction is required for release of the hammer for firing. Further, the arrangement of Roberts et al does not permit a compact, minimum volume package with the barometer in line with the firing pin and thus size and weight of the device are undesirably increased.
Accordingly, it is an object of the present invention to provide a controlled actuator mechanism that eliminates or minimizes the above mentioned disadvantages and achieves efficient, safe, reliable and precision operation in a compact package of small size and weight.